Engine torque may be controlled in a manner that regulates engine torque based on driver demand and vehicle operating conditions. Engine torque may be regulated in a number of ways. In one example, if an undesirable amount of wheel spin is detected spark angle may be retarded or cylinders may be deactivated to reduce the amount of engine torque and wheel slip.
One method to control torque during engine operation is described in U.S. Pat. No. 6,000,376. This method presents a means to dynamically control torque of an engine in some operating states. The method determines a driver torque demand from a pedal position sensor. An interpolation program, between a minimum torque value and a maximum torque value, interpolates the pedal position based torque. These values are predetermined and are preferably as least dependant on engine speed. In other words, desired driver torque is based on a predetermined, speed dependant, map of minimum and maximum torque.
The inventors herein have recognized that the above-mentioned method can have several disadvantages. Namely, the approach uses a map of torque values to determine the desired driver demand torque. The torque tables are based on a number of operating cylinders. Therefore, an engine that is capable of deactivating cylinders may need maps for each cylinder configuration. Further, engines capable of multi-stroke, e.g., six-stroke/twelve-stroke/two-stroke, and multiple valve configurations, e.g., an electromagnetically actuated valve engine, may require additional maps for each cylinder and valve permutation. The conceivable number of torque maps for an engine with valves that may be deactivated seems almost endless.
Another method, to control torque in an internal combustion engine is described in U.S. Pat. No. 6,247,445. The method regulates fuel mass injected into a combustion chamber based on a reference torque. The reference torque is a function of the torque demanded by the driver and further torque demands of an internal combustion engine. The torque demanded by the driver is determined from a pedal position sensor and other torque demands, such as a climate control system, are derived by changes in the speed of the internal combustion engine.
The inventors herein have also determined that this method may have a disadvantage. Namely, the method may not provide for accurate engine torque determination when an engine is operating with deactivated cylinders or with cylinders operating in a multi-stroke mode. For example, six-stroke cylinder mode and four-stroke cylinder mode may have unique friction and pumping losses. These losses may affect engine torque production and an improved engine torque determination may be made if they are included when determining engine torque.